Alternate high-low and root-fifth selection system for electrical musical instruments

ABSTRACT

A note selection system for a keyboard type electrical musical instrument which supplies to output leads the note signals corresponding to the highest and lowest notes of a group of notes played, or, in the alternative, the note signals corresponding to the musical root and fifth notes of certain three-note chords whenever only the three notes comprising each of these particular chords are played. The disclosed embodiment responds to playing any of four three-note chords in each of the 12 musical keys to supply the corresponding root and fifth note signals of these chords; if any other three-note chords, or other than three notes are played, the system supplies the highest and lowest note signals of the group of notes played.

schrecongost 4] ALTERNATE HIGH-LOW AND ROOT-FIFTH SELECTION SYSTEM FORELECTRICAL MUSICAL INSTRUMENTS [75] Inventor: Ray B. Schrecongost, ParkRidge,

lll.

. [73] Assignee: Hammond Corporation, Deerfield,

Ill.

22 Filed: Feb. 15, 1973 21 Appl. No: 332,642

[52] US. Cl 84/1.0l, 84/DIG. 2, 84/DIG. 22

[51] Int. Cl. ..G10h 1/00 [58] Field of Search 84/1.01, 1.03, 1.17,1.24,

84/DIG. 2, DIG. 22

[5 6] References Cited UNITED STATES PATENTS Young 84/l.l7

111 3,825,667. 1' July 23, 1974 3,708,604 l/1 973 Hebeisen et al.84/l.03 3,712,950 1/1973 Freeman 84/l.03

Primary Examiner-Richard B. Wilkinson Assistant Examiner-Stanley J.Witkowski Attorney, Agent, or Firm--Lowell C. Bergstedt s7 ABSTRACT Anote selection system for a keyboard type electrical musical instrumentwhich supplies to output leads the note signals corresponding to thehighest and lowest notes of a group of notes played, or, in thealternative, the note signals corresponding to the musical root andfifth notes of certain three-note chords whenever only the three notescomprising each of 1 these particular chords are played. The disclosedembodiment responds to playing any of four three-note chords in each ofthe 12 musical keys to supply the corresponding root and fifth notesignals of these chords; if any 3,305,620 2/1967 other three-notechords, or other than three notes are 3,546,355 12/1970 Maynard....84/1.03 played, the system supplies the highest and lowest 3,548,06612/1970 Freeman 84/l.03 note signals of the group of notes played3,590,129 6/1971 Freeman 84/1.0l 3,665,088 5/l972 Brandet al. 84/1.0l'10 Claims, 2 Drawing Figures 4 f Til/P55" KEYBOHRD N075 DEIZ'cToR c If?a a" v V q 1 neon amp? T0 Cb'QPpWA/Df' 071/62 GHTES CHORD HA/D" c4755 /f/j 11v /'7F77%q 45 9 0073 07 Z9 0 m Vl' i gmrp/vg MGM/JAIN Low c ewe/Pomam, 3: 2? 55 z o vz 554507 A P0074!!! qorpur 57 REFEIWVCE 64 {)3 GangsMfg/{f lls Cum/"s cam/17$ W57? 25 Z Y if 22 Q/A/PUT Q ken/ k T 600 0) 4/0077,!- r0 2/ I 59 (ls-x5002 1 v1 ALTERNATE HIGH-LOW AND RooT-EIETIISELECTION-SYSTEM FOR ELECTRICAL MUSICAL INSTRUMENTS BACKGROUND or THEINVENTION Keyboard type electrical musical instruments have incorporatedpreference circuits to select the note sig nals corresponding to thehighest; and lowest notes of a group of notes played, together withfrequency dividers, wave-shaping circuits and an automatic rhythmprogrammer in order to provide automatic bass accompanimentin'predetermined rhythmic patterns. See, for

example, the musical instrument rhythm system disclosed in Tennes andKern US. Pat. No. 3,567,838, and the high-low note preference systemsdisclosed in Bode US. Pat. No. 2,874,286, and in my copending patentapplication filed on 'July 17, 1972, having Ser. No. 272,437, andentitled D.C. KEYED HIGH LOW SE- LECT PREFERENCE SYSTEM FOR POLYPHONICELECTRICAL MUSICAL INSTRUMENTS now U.S. Pat. 'No. 3,766,305. A

However, when certain three-note chords of any given key are played suchasthe seventh or minor seventh chords, the use of the highest and lowestnotes for automatic bass accompanimentfrequently provides a lessmusically pleasing result than theuse of the musical root and fifthnotes of the chord played. For other combinations of notes, use ofbassnotes corresponding to the highest and lowest .notes of a group of notesplayed is, nevertheless, preferred as a simple and efficient method ofobtaining automatic bass accompani-' vment. Heretofore, no selectionsystem hasjbeen developed for providing both root and fifth notes of themost commonly played three-note chords or, in the. altemative, thehighest and lowest notes of any other played combination of notes.

SUMMARY or THE INvE TIoN .In brief, the present invention provides animproved note selection system for akeybo'ard type electrical musicalinstrument which 'supplies to output leads the note signalscorresponding to the root and fifth notes of selected three-noteaccompaniment chords, or, in the alternative, the note signalscorresponding to the highest and lowest notes of a group of notes playedif any other chords, or other than threenotes are played asaccompaniment. The present invention comprises: a high-low selectpreference system (of the order disclosed in the previously mentionedBode patent or my copending application), high and low note gating meansin circuit-with the preference system for connecting the highest andlowest note signals corresponding to a group of notes played to outputleads, a series of control means or, more specifically, chord AND gateswhich provide control voltages in responseto playing certain preselectedthree-note chords in any given key to root and fifth note gating meansfor connecting root and fifth note signals of these chords to the outputleads, and a three-note detector in a circuit to control each of thesetwo gating means, such that the root and fifth note gating means isoperated to provide the root and fifth note signals of a preselectedchord in response to control voltages from both a chord'AND gate and thethree-note detector whenever only the three notes of any of thepreselected chords are played, and the high and low note gating means isoperated to provide the. highest and lowest note signals of a group ofnotes played in response to a control voltage from the three-notedetector whenever other than three notes of any of the preselectedchords are played.

While the disclosed embodiment of the present invention will bedescribed in conjunction with electronic circuits employing conventionalPNP, type transistors,

the present invention is not limited to the use of these components butis particularly suitable for integrated circuit embodiments.

BRIEF DESCRIPTION OF- THE DRAWINGS FIG. 1 is a simplified diagrammaticrepresentation of the preferred embodiment of the present invention; and

' FIG. 2 is a schematic diagram which illustrates in detail the featuresof the present invention diagrammatically represented in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT signal sources representative ofnotes of the musical scale. As more fully described hereinafter, aseries of leads 11 connect the keys of keyboard 10 to control meansor,.more specifically, to 12 chord AND gates,

one for each. of the musical keys, typically illustrated for the C chordat 12. Since all of the chord AND gates function'identically, only theAND gate for the C chord is illustrated and described in detail. Thekeyboard 10 is also connected to a three-note detector 13 by means oflead 14. The three-note detector 13 is connected to all of the chord ANDgates by means of leads 17 connected to a common bus 16.

Each chord AND gate is connected to a corresponding root and fifth gatesin amanner similar to that illustrated for the C chord AND gate in FIG.l.- As shown in that figure, the C chord AND gate 12 is connected to theC chord root and fifth gates 18 by means of lead 19. A tone signalsource supplies the note signals corresponding to the root and fifthnotes of the C chord, namely C and G, to C chord root and fifth gates 18by means of leads 21 and 22 respectively. The C chord root and fifthgates 18 are further connected to all of the other chord root and fifthgates by means of leads 23 and 24, and to root and fifth output circuits26 by means of leads 27 and 28.

A high-low select preference system of the order disclosed in thepreviously mentioned Bode patent or my copending application,illustrated generally at 29, is in circuit with the keyboard 10 by meansof leads 30 and is connected to high and low output circuits 31 throughleads 32 and 33. This preference system operates to se lect the notesignals corresponding to the highest and lowest notes of a group ofnotes simultaneously played and connectsthese signals to high and lowoutput circuits 31 by means of leads 33 and 32 respectively. The

3 three-note detecting means 13 provides control voltages to root andfifth output circuits 26 and high and low output circuits 31 by means ofcontrol leads 34' and 36 respectively.

Root and fifth output circuits 26 and high and low output circuits'31are interconnected by means of leads 37 and 38 such that, when thesystem operates, either the root or low note will appear on lead 37 andeither the fifth or high note will appear on lead 38. Lead 37 isconnected to root-low output 39 by means of lead 41, and lead 38 isconnected to fifth-high output 42 by means of lead 43. These outputterminals can be connected to frequency dividers, desired wave-shapingcircuits'and an automatic rhythm programmer in order to provideautomatic bass accompanimentto notes played on the keyboard as diclosed,for example, in the previously mentioned Tennes and Kern patent.

The high and low output circuits 31 are controlled by three-notedetector 13 by means of a voltage on lead 36 to connect the lowest andhighest note signals to leads 37 and 38 respectively. However, whencertain three-note chord combinations are played on keyboard 10, thepresent invention operates to connect the root and fifth note signals ofthe particular chord played from root and fifth output circuits 26 toleads 37 and 38 respectively in place of the lowest and highest notesignals.

The preferred embodiment illustrated in FIGS. 1 and 2 contains 12 chordAND gates which respond to four chords in each musical key. Asillustrated in FIG. 1, the C chord AND gate 12 is connected to the keysof said keyboard corresponding to the notes C, D E, G and .A whichcomprise the four most common chords in the key of C: C major (CEG), Cminor (CD #G), C seventh (CEA# and C minor seventh (CD "A Whenever anyofthese three-note combinations are played on-keyboard 10, the C chordAND gate 12 and three-note detector 13 cooperatively operate to connectthe root and fifth notes of a C chord, namely C and G, to leads 37 and38 respectively instead of the highest and lowest note signals of any ofthese combinations played. In response to playing any of theforegoing'combinations, the C chord AND gate '12 provides a controlvoltage to C chord root and fifth gates 18..The three-note detector 13,utilizing input voltages from keyboard 10 on lead 14 and the C chord ANDgate 12 on lead 16, operates the root and fifth output circuits 26 bymeans of a control voltage on lead 34 whenever only the three notes ofeither the C major, C minor, C seventh or C minor seventh chords areplayed. The C chord root and fifth gates 18 and the root and fifthoutput circuits 26 are cooperatively operable to provide the root andfifth note signals to leads 37 and 38 respectively only when controlvoltages are present both on leads l9 and 34 in response to operation ofboth the C chord AND gate 12 and the threenote detector 13 respectively.If chords other than the C major, C minor, C seventh or C minor seventhare played on keyboard 10, the C chord AND gate 12 will not provide acontrol voltage on lead 19 to operate C chord root and fifth gates 18.Further, if other than three notes of any'of these chords are played onkeyboard 10, three-note detector 13 will not provide a control voltageon line 34 to operate root and fifth output circuits 26. Only when bothconditions are satisfied, namely, operation of the C chord gate 12 toprovide a control voltage on lead 19 and operation-of three-notedetector 13 to provide a control voltage on lead 34 will the root andfifth note signals be connected to leads 37 and 38 in place of thelowest and highest note signals from the high and low output circuits31. Chord AND gates and chord root and fifth gates corresponding tochords in other keys function in a similar manner.

With additional reference to FIG. 2, the operation of the electroniccircuits diagrammatically represented in FIG. 1 will now be described indetail. As shown in FIG. 2, keyboard 10 comprises a series of keys orswitches 50, representative of notes of the musical scale, whichcomplete DLC. circuits connecting D.C. bus 51 to tone signal keyers (notillustrated) by means of leads 52 (shown only for one C note), groundedload resistors 53 through isolating diodes 54 (shown only for the B andC notes), and to chord AND gates (typified by C chord AND gate 12) bymeans of leads 11. It should be recognized that, for purpose ofsimplification, only those leads 11 from keys 50 corresponding to the C,D E, G and A notes have been illustrated, but the disclosed embodimentcontains similar connections (not illustrated) from corresponding keys50 to other chord AND gates for the major, minor, seventh and minorseventh chords in each of the other eleven keys. Furthermore, only aportion of a typical keyboard, corresponding to the accompanimentsection rather than the solo section, is illustrated in FIG. 2, againfor simplification. Diodes 54 and resistors 53 together comprise ORgates for octavely related keyswitches so that chords can be played inroot position or various inversions.

Each of the leads 11 is connected through resistor 56 to a correspondingtransistor in the C chord AND gate 12. Leads 11 from ke-ys 50corresponding to notes G and A are connected to transistors 57 and 58respectively. The collectors of each of these transistors are connectedto a DC. supply 59, and their emitters are connected together and to thecollectors of transistors 61 and 62, which are connected through leads11 to keys 50 corresponding respectively to notes D and E. The keycorresponding to the note C is likewise connected to transistor 63,which has its collector connected to the emitters of transistors 61 and62. The emitter of transistor 63 is connected to lead 17 through diode15, to lead 19 through resistor 64 and then to ground through resistor66. Each chord AND gate, therefore, has three series-connected elements,two of such elements each having another element connected in parallel,to provide four possible combinations of operation of threeseries-connected elements. All of the transistors in the C chord ANDgate 12 are normally biased for cutoff operation. However,simultaneously playing any of the four combinations of keys 50corresponding to notes C, E and G (C major chord); or C, D and G (Cminor chord); or C, E and A (C seventh chord; or C, D and A (C minorseventh) operate the C chord AND gate 12 to provide a control voltage onlead 19 from DC. supply 59 in response to simultaneous conduction ofthree series-connected transistors biased into saturation from DC. bus51. The C chord AND gate responds to playing the four indicated chordsin the key of C, and the other chord AND gates similarly respond toplaying either the major, minor, seventh or minor seventh chords intheir respective keys.

A control voltage on line 19 operates to connect the root and fifthnotes of a C chord to leads 27 and 28 respectively by operation of the Cchord root and fifth gates 18. Lead 19 is connected to transistors 68and 69 through diodes 71 and 72 respectively. The emitter of transistor68 is connected to C note signal input 78 through resistor 79 and toground through resistor 81.

Similarly, the emitter of transistor 69 is connected to G note signalinput 82 through resistor 83, and to ground through resistor 84. Anyconvenient tone signal sources can be connected to'the 'root and'fifthinputs of the root fifth note signals present on leads 27 and 28 toleads 37 and 38, and to respective outputs 39 and 42. Therefore, inorder to obtain root and fifth note signals at the outputs 39 and 42,itis necessary to have control voltages present on both lead 19 (fromthe C chord AND gate 12) and on lead 34 (from the three-note detector13). If either of these control voltages is absent, the note signals.corresponding to the lowest and highest notes of a group of notesplayedwill be connected toleads 37 and 38, and to respective outputs 39 and42.

The high-low select preference system 29 is connected to the emitters.of transistors 93 and 94 by means of leads 32 and33 respectively.Lead'36 from the three-note detector 13 is connected to the bases oftransistors 93 and-94 through resistors 98 and 99. The presence of acontrol voltage on lead 36 operates to bias normally cutoff transistors93 and 94 to key the lowest and highest note signals present on leads 32and 33 to leads 37 and 38. When three notes are played which operate oneof the chord AND gates, the threenote detector 13 will not provide acontrol voltage on lead 36, but instead will provide a control voltageon lead 34 to operate theroot and fifth output circuits 26 to key theroot and fifth note signals of the chord played to the output leads.

It should be noted that, because isolating diodes 54 couple octavelyrelated notes, more than three keys 50 may be played to provide the rootand fifth bass notes of a chord as long as the additional notes areoctavely related to any of the three notes which operate one of thechord AND gates. However, when notes are played which do not operate oneof the chord AND. gates, the system provides bass notes corresponding tothe highest and lowest of the actual notes played, within the limits ofthe high-low preference system 2 One side of the interconnectedisolating diodes 54 of keyboard is connected to a diode 101 in serieswith a resistor'102 (shown only for B and C notes) corresponding to eachof the twelve keys. All of the resistors 102 are connected together andto lead 14 at junction 103, which itself is grounded through resistor104. The voltage inputs necessary to operate the three-note detector 13are provided by lead 14 from the keyboard 10 and lead 16 connected toeach of the chord AND gates through leads 17 and diodes 15.

Lead 14 is connected to the base of transistor 107 of the three-notedetector 13 through three seriesconnected diodes 108, and to the base oftransistor 111 by means of two series-connected diodes 112 and resistor113. The collector of transistor 107 is connected to the base oftransistor 111 by means of diode 115. The collector of transistor 111 isconnected to the base of transistor 116 through resistor 117, and thecollector of transistor 116 is in turn connected to the base oftransistor 118 through resistor 119. Collectors of transistors 107, 111and 116 are connected to DC. input 121 by'rneans of resistors 122. Thecollector of transistor 118 is connected to DC. input 123 throughresistor 124 and to ground through series connected resistors 126 and127. The emitter of transistor 118 is directly connected to thecollector of transistor 128 to form an AND gate in conjunction withtransistor 118. The base of transistor 128 is connected to lead 16through resistor 129, and its emitter is connected to lead 34 and thento ground through resistor 131. The junction of resistors 126 and 127 isconnected to the base of transistor 132 through diode 133. The collectorof transistor 132 is connected to its base through resistor 134 and toDC. input 136. The emitter of transistor 132 is connected to lead 36 andto ground through resistor 137. 1

The values of resistors 102 (10,000 ohms) and 104 (270 ohms) are chosensuch that, in conjunction with the resistances of the seriescombinations of diodes 108 and 112 and 10,000 ohm resistor 113,transistor 111 is biased into a conducting state whenever three or morekeys S0 of keyboard 10 are played, and transistor 107 is operativelybiased to conduct whenever four or more keys50 are played. Bothtransistors 107 and 111 are, however, otherwise nonconducting with theresult that transistor 116 is normally conducting because of bias fromDC. input 121. Playing only three keys 50 operates to bias transistor111 into conduction, which operates to turn transistor 116 off bygrounding its own bias input. Playing four keys will operate to biastransistor 107 into conduction, which results in turning transistor 111off by grounding its bias input through inhibiting diode 114. Therefore,transistor 116 will be biased to cutoff only when transistor 111 isconducting in response to playing only three keys 50; if any othernumber of keys are played, transistor 116 will remain in a conductingstate.

It should be noted that whenever transistor 116 is conducting,transistor 118 will be biased into cutoff by grounding its bias input.Only when exactly three keys 50 are played will transistor 111 beconducting, thereby. turning transistor 116 off, resulting in conductionof transistor 118. Transistors 118 and 128 form an AND gate to provide acontrol voltage on line 34 from DC. input 123 to root and fifth outputcircuits 26 whenever both transistors 118 and 128 are conducting.Transistor 128 will conduct whenever a control voltage is present onlead 16 in response to operation of any chord AND gate. Whenever exactlythree keys are played and those three keys correspond to any of thethree-note combinations operable to cause a chord AND gate to conductwill the root and fifth output circuits be operated by a control voltageon line 34. In that case, when both transistors 118 and 128 areconducting, transistor 132 will be biased into cutoff by grounding itsbias input, with the result that no control voltage will appear on lead36 to the high and low output circuits 31. Whenever either or bothtransistors 118 or .128 are off, transistor 132 will conduct to providea control voltage to lead 36 from D.C. input 136 because of biasingresistor 134 (470,000 ohms). Transistor 132 will conduct to provide acontrol voltage on lead 36 to operate the high and low output circuitswhenever other than three of the keys 50 are played, or whenever anythree-note chords are played which do not operate any of the chord rootand fifth gates.

I claim:

1. In an electrical musical instrument:

a plurality of switching elements, each being selectably actuated forkeying one of the notes of the musical scale; I

a plurality of chord logic gates, each coupled to a preselectedcombination ofsaid switching elements and providing an output signalupon actuation of selected subcombinations thereof representing aparticular set of chords having at least a common root note;

a plurality of chord tone gating means, each coupled to one of saidchord logic gates and being adapted to gate at least one tone signalcorresponding to said commonroot note in response to said output signal.

2.Apparatus as claimed in claim 1, wherein each of said chord logicgates is associated with a particular set of chords having both a commonroot and a common fifth note; and each-of said chord tone gating meanscomprises two tone signal gates for separately gating two tone signalscorresponding to said common root and fifth notes.

3. Apparatus as claimed in claim 2, further compristhree-note detectormeans comprising: discriminator circuit means coupled to said switchingelements for producing a discriminator output signalif and only ifswitching elements corresponding to three separate notes are actuated,and coincidence circuit means coupled. to saiddiscriminator circuitmeans and each of said chord logic gates for signalling coincidence ofsaid discriminator output signals and one of said output signals fromsaid chord logic gates; and

.gating circuit means receiving each of said root and fifth tone signalsfrom said chord tone gating means for gating said root and fifth tonesignals in response to said coincidence signal.

4. Apparatus as claimed in claim 3, further comprisa tone signalpreference system coupled to said switching elements for selectivelygating high and low tone signals corresponding to the highest and lowestnotes keyed by said switching elements; and

said gating circuit means further receiving said high and low tonesignals for gating the same in absence of said coincidence signal.

5. Apparatus as claimed in claim 2, wherein each of said chord logicgates is coupled to switching elements representing associated root,major third, minor third, fifth, and seventh notes of a particular setof chords and comprises logic gating means for producing an output ifswitching elements corresponding to one of the following subcombinationsof notes are actuated:

a. root, major third, fifth;

b. root, minor third, fifth;

c. root, major third, seventh; and

d. root, minor third, seventh.

6. Apparatus as claimed in claim 5, wherein said logic gating meanscomprises:

a first transistor having its base electrode coupled to a switchingelement representing a root note;

a first pair of transistors having emitter and collector electrodesconnected in common and base electrodes separately connected toswitching elements representing major third and minor third notes; and

a second pair of transistors having emitter and collector electrodesconnected in common and base electrodes separately connected toswitching elements representing fifth and seventh notes;

said first transistor and said first and second pair of transistorsbeing coupled in series between a source of D.C. bias and groundreference such that coincident operation of said first transistor and atleast one transistor in each of said first and second pairs produces anoutput signal from said chord logic gate.

7. In an electronic musical instrument:

a set of switching elements, each being selectably actuated for keyingone of the notes of the musical scale over at least a two-octave range;

a set of logic OR gates, each associated with one of the notes of themusical scale and having inputs coupled to octavely related switchingelements associated with said note;

a plurality of chord logic gates, each coupled to a preselectedcombination of said OR gates and producing an output signal uponactuation of switching elements associated with selected subcombinationsof notes representing a particular set of chords having common root'andfifth notes;

a plurality of pairs of chord tone gates, each pair coupled to one ofsaid chord logic gates for gating tone signals corresponding to commonroot and fifth notes in response to said output signal;

circuit means. coupled to said set of OR gates for de veloping a D.C.voltage corresponding to the number of OR gates actuated and thereby tothe number of different notes being keyed by said switching elements;

a three-note detector comprising a discriminator circuit receiving saidD.C. voltage and producing a discriminator output signal if and only ifthree different notes are being keyed and a coincidence circuit coupledto said discriminator circuit and each of said chord logic. gates forproducing a control signal upon coincidence of said discriminator outputsignal and-an output signal from one of said chord logic gates;

a pair of output gatecircuits each receiving in common respective rootand fifth note tone signals from said chord tone gates and gating saidtone signals to a pair of output leads in response to said controlsignal.

8. Apparatus as claimed in claim 7, wherein said three-note detectorfurther comprises a control circuit coupled to said coincidence circuitfor producing a second control signal in the absence of said firstcontrol signal; and further comprising:

a tone signal preference system coupled to said switching elements forselectively gating high and low tone signals corresponding to thehighest and 7 lowest noteskeyed said switching elements; and

" a second pair of output gate circuits each receiving 9. In anelectronic musical instrument:

a plurality. of switching elements, each being selectably actuated forkeying one of the notes of the musical scale;

a plurality of chord logic gates, each coupled to a preselectedcombination of said switching elements and providing an output signalupon actuation of selected subcombinations thereof representing aparticular set of chords having common root and fifth notes;

a plurality of sets of chord tone gates, each coupled to one of saidchord logic gates for gating tone signals corresponding to said commonroot and fifth notes; I

discriminator circuit means coupled to said switching elements forproducing a discriminator output signal if and only if switchingelements corresponding to three separate notes are actuated;

coincidence circuit meanscoupled to said discriminator circuit means andeach of said chord logic gates for producing a first control signal uponcoincidence of said discriminator output signal and one of said outputsignals from said chord logic gates and a second control signal in theabsence of said first control signal;

a tone signal preference system coupled to said switching elements forselectively gating high and low tone signals corresponding to thehighest and lowest notes keyed by said switching elements; and

gating circuit means receiving said root and fifth tone signals and saidhigh and low tone signals and responsive to said first control signal togate said root and fifth tone signals, respectively, to first and sec-0nd output leads and responsive: to said second control signal to gatesaid low and high tone signals, respectively, to said first and secondoutput leads.

10. Apparatus as claimed in claim 9, wherein said gating circuit meanscomprises first and second pairs of transistor gates; a first transistorin each pair receiving, respectively, said root and low tone signals atemitter electrodes and said first and second control signals at baseelectrodes, and having commoned collector electrodes connected to saidfirst output lead; a second transistor in each pair receiving,respectively, said fifth and high tone signals at emitter electrodes andsaid first and second control signals at base electrodes, and havingcommoned collectors connected to said second output lead.

1. In an electrical musical instrument: a plurality of switchingelements, each being selectably actuated for keying one of the notes ofthe musical scale; a plurality of chord logic gates, each coupled to apreselected combination of said switching elements and providing anoutput signal upon actuation of selected subcombinations thereofrepresenting a particular set of chords having at least a common rootnote; a plurality of chord tone gating means, each coupled to one ofsaid chord logic gates and being adapted to gate at least one tonesignal corresponding to said common root note in response to said outputsignal.
 2. Apparatus as claimed in claim 1, wherein each of said chordlogic gates is associated with a particular set of chords having both acommon root and a common fifth note; and each of said chord tone gatingmeans comprises two tone signal gates for separately gating two tonesignals corresponding to said common root and fifth notes.
 3. Apparatusas claimed in claim 2, further comprising: three-note detector meanscomprising: discriminator circuit means coupled to said switchingelements for producing a discriminator output signal if and only ifswitching elements corresponding to three separate notes are actuated,and coincidence circuit means coupled to said discriminator circuitmeans and each of said chord logic gates for signalling coincidence ofsaid discriminator output signals and one of said output signals fromsaid chord logic gates; and gating circuit means receiving each of saidroot and fifth tone signals from said chord tone gating means for gatingsaid root and fifth tone signals in response to said coincidence signal.4. Apparatus as claimed in claim 3, further comprising: a tone signalpreference system coupled to said switching elements for selectivelygating high and low tone signals corresponding to the highest and lowestnotes keyed by said switching elements; and said gating circuit meansfurther receiving said high and low tone signals for gating the same inabsence of said coincidence signal.
 5. Apparatus as claimed in claim 2,wherein each of said chord logic gates is coupled to switching elementsrepresenting associated root, major third, minor third, fifth, andseventh notes of a particular set of chords and comprises logic gatingmeans for producing an output if switching elements corresponding to oneof the following subcombinations of notes are actuated: a. root, majorthird, fifth; b. root, minor third, fifth; c. root, major third,seventh; and d. root, minor third, seventh.
 6. Apparatus as claimed inclaim 5, wherein said logic gating means comprises: a first transistorhaving its base electrode coupled to a switching element representing aroot note; a first pair of transistors having emitter and collectorelectrodes connected in common and base electrodes separately connectedto switching elements representing major third and minor third notes;and a second pair of transistors having emitter and collector electrodesconnected in common and base electrodes separately connected toswitching elements representing fifth and seventh notes; said firsttransistor and said first and second pair of transistors being coupledin series between a source of D.C. bias and ground reference such thatcoincident operation of said first transistor and at least onetransistor in each of said first and second pairs produces an outputsignal from said chord logic gate.
 7. In an electronic musicalinstrument: a set of switching elements, each being selectably actuatedfor keying one of the notes of the musical scale over at least atwo-octave range; a set of logic OR gates, each associated with one ofthe notes of the musical scale and having inputs coupled to octavelyrelated switching elements associated with said note; a plurality ofchord logic gates, each coupled to a preselected combination of said ORgates and producing an output signal upon actuation of switchingelements associated with selected subcombinations of notes representinga particular set of chords having common root and fifth notes; aplurality of pairs of chord tone gates, each pair coupled to one of saidchord logic gates for gating tone signals corresponding to common rootand fifth notes in response to said output signal; circuit means coupledto said set of OR gates for developing a D.C. voltage corresponding tothe number of OR gates actuated and thereby to the number of differentnotes being keyed by said switching elements; a three-note detectorcomprising a discriminator circuit receiving said D.C. voltage andproducing a discriminator output signal if and only if three differentnotes are being keyed and a coincidence circuit coupled to saiddiscriminator circuit and each of said chord logic gates for producing acontrol signal upon coincidence of said discriminator output signal andan output signal from one of said chord logic gates; a pair of outputgate circuits each receiving in common respective root and fifth notetone signals from said chord tone gates and gating said tone signals toa pair of output leads in response to said control signal.
 8. Apparatusas claimed in claim 7, wherein said three-note detector furthercomprises a control cirCuit coupled to said coincidence circuit forproducing a second control signal in the absence of said first controlsignal; and further comprising: a tone signal preference system coupledto said switching elements for selectively gating high and low tonesignals corresponding to the highest and lowest notes keyed by saidswitching elements; and a second pair of output gate circuits eachreceiving one of said high and low tone signals and gating said tonesignals to said pair of output leads in response to said second controlsignal.
 9. In an electronic musical instrument: a plurality of switchingelements, each being selectably actuated for keying one of the notes ofthe musical scale; a plurality of chord logic gates, each coupled to apreselected combination of said switching elements and providing anoutput signal upon actuation of selected subcombinations thereofrepresenting a particular set of chords having common root and fifthnotes; a plurality of sets of chord tone gates, each coupled to one ofsaid chord logic gates for gating tone signals corresponding to saidcommon root and fifth notes; discriminator circuit means coupled to saidswitching elements for producing a discriminator output signal if andonly if switching elements corresponding to three separate notes areactuated; coincidence circuit means coupled to said discriminatorcircuit means and each of said chord logic gates for producing a firstcontrol signal upon coincidence of said discriminator output signal andone of said output signals from said chord logic gates and a secondcontrol signal in the absence of said first control signal; a tonesignal preference system coupled to said switching elements forselectively gating high and low tone signals corresponding to thehighest and lowest notes keyed by said switching elements; and gatingcircuit means receiving said root and fifth tone signals and said highand low tone signals and responsive to said first control signal to gatesaid root and fifth tone signals, respectively, to first and secondoutput leads and responsive to said second control signal to gate saidlow and high tone signals, respectively, to said first and second outputleads.
 10. Apparatus as claimed in claim 9, wherein said gating circuitmeans comprises first and second pairs of transistor gates; a firsttransistor in each pair receiving, respectively, said root and low tonesignals at emitter electrodes and said first and second control signalsat base electrodes, and having commoned collector electrodes connectedto said first output lead; a second transistor in each pair receiving,respectively, said fifth and high tone signals at emitter electrodes andsaid first and second control signals at base electrodes, and havingcommoned collectors connected to said second output lead.